The present invention relates to a fuel assembly, and more particularly to a fuel spacer of round cell type suitable for boiling water reactors, and a fuel assembly employing the fuel spacer.
Generally, a fuel assembly for use in boiling water reactors comprises a plurality of fuel elements and a water rods. These fuel elements and water rods are bundled by a plurality of fuel spacers into a square grid pattern with a certain spacing left between adjacent twos. Also, these fuel elements and water rods are held by an upper tie plate and an a lower tie plate at respective ends to make up a fuel bundle which is housed in a channel box.
One example of such fuel spacers is a fuel spacer of round cell type that fuel elements are supported by being inserted to a plurality of cylindrical members (round cells). The fuel spacer of round cell type is constructed by arranging round cells in a grid pattern in a mutually contacting relation, and joining the adjacent round cells together by welding. A fuel element inserted to each of the round cells is radially supported by two projections formed by projecting parts of the round cell inwardly, and springs. The springs are provided in such a manner as to penetrate upper and lower openings formed in two round cells in a position where the two round cells contact each other, and to project into both the round cells.
The following prior arts, for example, are known as being related to fuel spacers of round cell type.
(1) JP, A, 59-65287 PA0 (2) JP, B, 3-76879 PA0 (3) JP, A, 5-150072 PA0 (4) JP, A, 2-221891
In fuel spacers described in these prior arts (1) and (2), a loop-like spring comprising a pair of opposed leaf springs and arcuate coupling members for coupling the leaf springs at their upper and lower ends is assembled in a round cell.
In a fuel spacer described in this prior art (3), a pair of opposed leaf springs are coupled to each other at their upper and lower ends by a flat semi-annular coupling members.
In a fuel spacer described in this prior art (4), coupling members for coupling a pair of opposed leaf springs at their upper and lower ends are provided with upper and lower ears which are respectively embraced by upper and lower embracing portions provided on an outer peripheral surface of a round cell.